1. Shares acquired based on performance targets for the August 2, 2010, August 1, 2011, and November 9, 2011 awards of Restricted Stock Units.

2. Shares acquired upon vesting of the August 2, 2010, August 1, 2011, and November 9, 2011 awards of service-based Restricted Stock Units.

3. This transaction was executed pursuant to a Rule 10b5-1 trading plan, in multiple trades at prices ranging from $93.26 to $94.14. The reported price is the weighted average sale price. The reporting person undertakes to provide to the Company, any security holder of the Company, or Securities and Exchange Commission staff, upon request, complete information regarding the number of shares sold at each separate price.

4. Each Restricted Stock Unit represents a contingent right to receive one share of F5 Networks, Inc. Common Stock on the vest date.

6. If the reporting person continues to serve as an officer of the Company on the vest date, the corresponding number of shares of Common Stock of F5 Networks, Inc. will be issued to the reporting person on the vest date.